diff --git a/_quarto.yml b/_quarto.yml
index f398d797..06773646 100644
--- a/_quarto.yml
+++ b/_quarto.yml
@@ -192,3 +192,9 @@ book:
       - part: "Acknowledgments"
         chapters:
           - src/credits/credits.md
+
+format:
+  html:
+    theme:
+      light: default
+      dark: darkly